The Morula and Blastocyst

Script: By 3 to 4 days after fertilization, the dividing cells of the embryo assume a spherical shape and the embryo is called a morula.

By 4 to 5 days, a cavity forms within this ball of cells and the embryo is then called a blastocyst.

The cells inside the blastocyst are called the inner cell mass and give rise to the head, body, and other structures vital to the developing human.